Permafrost melting

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Scientists have been issuing warnings for over a decade about permafrost in the Artic melting and releasing vast amounts of carbon dioxide and methane into the atmosphere. The release of millions of tonnes of greenhouse gases previously "stored" in permafrost could create a "tipping point" for runaway climate change such that global temperatures could increase up to 4 to 6C.

Permafrost is a deep layer of frozen soil covering about a quarter of landmass in the northern hemisphere, and is thought to contain twice the amount of carbon already in the atmosphere.

Permafrost stores carbon dioxide, but it also has lots of little microbes in it and lots of organic matter. When that organic matter isn't frozen any more, it gets broken down by microbes in the soil and under certain circumstances that breakdown process releases a lot of methane.

The United Nations Environment Program released a report in November 2012 indicating that the world's permafrost is beginning to thaw, bringing with it the threat of a big increase in global warming by 2100.

A global temperature increase of 3°C means a 6°C increase in the Arctic, resulting in anywhere between 30 to 85 per cent loss of near-surface permafrost. Such widespread permafrost degradation will permanently change local hydrology, increasing the frequency of fire and erosion disturbances.

The report states that warming permafrost could:

Release the equivalent of between 43 and 135 billion tonnes of carbon dioxide, the main greenhouse gas, by 2100, up to 39 per cent of annual emissions from human sources.

Emit 43 to 135 Gt of CO2 equivalent by 2100 and 246 to 415 Gt of CO2 equivalent by 2200.

Damage to critical infrastructure, such as buildings and roads, will incur significant social and economic costs.